Explosive composition containing a glycol and guar gum ether

ABSTRACT

A GELATINIZED EXPLOSIVE COMPOSITION COMPRISING A HIGH ENERGY SENSITIZER AND FROM ABOUT 3% TO ABOUT 50% BY WEIGHT OF A NON-EXPLOSIVE GEL COMPRISING AT LEAST ONE LOWER ALIPHATIC GLYCOL SELECTED FROM THE GROUP CONSISTING OF ETHYLENE GLYCOL, DIETHYLENE GLYCOL, PROPYLENE GLYCOL AND DIPROPYLENE GLYCOL THICKENED WITH A MATERIAL SELECTED FROM THE GROUP CONSISTING OF HYDROXYETHYL AND HYDROXYPROPYL ETHERS OF POLYSACCHARIDES AND MIXTURES THEREOF.

"United States Patent m 3,730,790 EXPLOSIVE COMPOSITION CONTAINING A GLYCOL AND GUAR GUM ETHER Errol Linton Falconer and Gerhard Franz Otto Karl Finch, Mont Saint-Hilaire, Quebec, Canada, assignors to Canadian Industrial Limited, Montreal, Quebec, Canada No Drawing. Filed Feb. 29, 1972, Ser. No. 230,520 Int. Cl. C06b 1/04 US. Cl. 149-44 4 Claims ABSTRACT OF THE DISCLOSURE A gelatinized explosive composition comprising a high energy sensitizer and from about 3% to about 50% by weight of a non-explosive gel comprising at least one lower aliphatic glycol selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol and dipropylene glycol thickened with a material selected from the group consisting of hydroxyethyl and hydroxypropyl ethers of polysaccharides and mixtures thereof.

The present invention relates to explosive compositions of the gelatinous and semi-gelatinous types which are devoid of any liquid nitric ester sensitizer. More particularly, the invention relates to a novel gel-phase system which may be employed in gelatinous and semi-gelatinous explosives.

Commercial gelatinous and semi-gelatinous high explosives which are known as gelatin dynamites or semigelatin dynamites, are plastic or cohesive in character and consists of nitroglycerin or other liquid nitric ester gelatinized with nitrocellulose, which gel-phase is blended with other ingredients including oxidizing agents, carbonaceous ingredients and the like to form finished explosive mixtures. Such explosives may be prepared in a wide range of strengths and with a variety of physical characteristics and consequently may be tailored for specific end uses. The degree or extent of cohesiveness of such mixtures will largely depend on the quantity of liquid nitric ester/ nitrocellulose sensitizer gel-phase present. The highly viscous gelatin dynamites of high strength will contain larger quantities of sensitizer than will the lower strength less cohesive semi-gelatin dynamites.

These successful gelatin and semi-gelatin dynamites have enjoyed wide commercial acceptance because of their economy, high strength, good water resistance and ease of manufacture and use. They are, however, not without disadvantages, the most important of which being their sensitivity to inadvertant detonation from shock or impact and the evolution of vapors of the liquid nitric esters which causes a toxic response in certain exposed individuals.

-A number of efforts have been made in the past to moderate the undesirable characteristics of the liquid nitric ester sensitized gelatins and semi-gelatins by the inclusion therein of a number of diluents, extenders and desensitizers. Nitro aromatic compounds such as dinitrotoluene which are miscible with nitric esters have been of some assistance in reducing sensitivity to mechanical impact but only minor amounts of these may be included because of low solubility characteristics and high oxygen demand. The prior art describes the use of moderating materials such as glycerin thickened with animal glue, cellulose pitch syrup, waste sulphite liquors and saturated calcium nitrate solutions. The addition of water/ oil emulsions, mineral oils and polysilicone gels has also been suggested. Most of these attempts have failed commercially because of various inadequacies.

It has now been found that excellent gelatinous and semi-gelatinous explosives may be made which possess 3,730,790 Patented May 1, 1973 all of the desirable characteristics of conventional gelatin explosives and yet which are devoid of any liquid nitric ester.

Generally described, the explosives of the present invention which are gelatinized high explosive compositions comprise at least one high energy sensitizer and from about 3% to about 50% by weight of a non-explosive gel comprising at least one lower aliphatic glycol selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol and dipropylene glycol thickened with a material selected from the group consisting of hydroxyethyl and hydroxypropyl ethers of polysaccharides and mixtures thereof.

While a number of polymeric and other colloidal thickeners for fluids are known and may be partly etfective in thickening or gelling lower aliphatic glycols, they are generally unsuitable for use in conjunction with oxygensupplying salts found in nearly all gelatinous explosive mixtures. For example, the inorganic colloidal thickeners such as pyrogenic silica results in unsatisfactory explosive products in terms of exudation. Soluble polymers such as polyoxyethylene resins are salt sensitive and are precipitated in the presence of dissolved oxygen salts. Only the series of the hydroxyethyl and hydroxypropyl ethers of polysaccharides have been found capable of providing non-exuding stable lower glycol gels in the presence of oxidizing salts such as ammonium, sodium and calcium nitrates and perchlorates. The quantity of thickener employed with a given quantity of lower glycol is arbitrary and depends on the degree of thickness or plasticity desired. Generally from 0.2% to 10.0% by weight of thickener in the glycol can be used although the higher level will most often be beyond the degree of gelation normally useful in commercial explosives cartridged with conventional cartridging machines. Examples of polysaccharides the hydroxyethyl and hydroxypropyl ethers of which are suitable for use as thickener are glucose polysaccharides, mannose polysaccharides and galactose polysaccharides.

The following examples and tables illustrate the gelphase system of the invention and will show the desirable properties of gelatinous and semi-gelatinous explosive compositions containing the same.

EXAMPLE 1 Two gelling tests A and B were undertaken to evaluate the ability of several hydroxyalkyl ethers of polysaccharides to thicken ethylene glycol.

In test A, 10 grams of ethylene glycol and 1 gram of a polysaccharides derivative were mixed at room temperature in the presence of 5 grams each of sodium nitrate and ammonium nitrate. These nitrates are typical of those found in commercial explosive compositions. A plasticlike self-supporting gel was formed as follows:

with hydroxyethyl guar, after 5 minutes with hydroxypropyl guar, after 15 minutes with hydroxyethyl cellulose, after 30 minutes In test B, a salt-containing glycol-based liquor was prepared by dissolving 60 parts of technical grade calcium nitrate and 30 parts of ammonium nitrate in 55 parts of ethylene glycol, 23 parts of diethylene glycol and 25 parts of formamide, a useful fuel ingredient All salts were fully dissolved at room temperature. About one gram of a polysaccharide derivative was added to 10 grams of the glycol-based liquor. Plastic-like self-supporting gels were formed as follows:

with hydroxyethyl cellulose, after 3 minutes with hydroxyethyl guar, after 6 minutes with hydroxypropyl guar, after 30 minutes Observation of the results of tests A and B emphasizes the unpredictability of the influence of soluble salts on the rates at which the gelling of the ethylene glycol liquor phase takes place. It can be observed, for example, that hydroxyethyl cellulose in test A produced a gelled glycol in 30 minutes in the presence of ammonium and sodium nitrate, while in test B the same thickener produced a gel in about 3 minutes in the presence of calcium and ammonium nitrate and formarnide. The degree of gelation and the time in which it occurs is also effected by the degree of substitution (D.S.) as outlined by W. A. Jordan in U.S. Pat. No. 3,483,121, issued on Dec. 9, 1969. It was generally observed that the guar derivatives produced a clearer gel than did the cellulose derivatives but all the gel types of the tests were useable in a wide range of explosive formulations.

In similar tests propylene glycol and diethylene glycol were gelled by the addition of hydroxyethyl guar. Hydroxypropyl guar, hydroxypropyl cellulose and hydroxyethyl starch were found capable of gelling glycol solutions of oxidizer nitrate salts. Surprisingly, it was noted that hydroxypropyl guar did not gel pure glycol. Only when salts were dissolved in the glycol did the hydroxypropyl guar produce effective thickening. Most of these thickening agents are generally available from commercial suppliers but, if desired, may be prepared in the laboratory or factory. Hydroxyethyl starch, for example, may be made be reacting equimolar proportions of corn starch, 2-chloroethanol and 40% sodium hydroxide in the presence of isopropanol. This preparation is typical of the preparation of hydroxyethyl derivatives of polysaccharide compounds described in the chemical literature.

The most useful of the gel-phase matrices for use in gelatin or semi-gelatin explosive compositions are those having relatively the least negative oxygen values. The lower aliphatic glycol liquid component of the gel-phase matrix of the present invention has a large oxygen demand for complete combustion. For example, ethylene glycol and propylene glycol have oxygen values respectively of -129, 151, and --168. Less negative values than those exemplified would be advantageous in the design of explosives. In order to provide a liquid component of more suitable oxygen balance for the gel matrix, for gelatin and semi-gelatin compositions, a lower aliphatic glycol liquor may be prepared which remains liquid at normal or slightly elevated temperatures. A series of such liquors are shown in Table I below. These mixtures may be described as glycol-based solutions of oxidizer salts or lower amine nitrates. While nitrate salts are shown in the table, perchlorate salts such as sodium, calcium and ammonium perchlorate may also be employed since these perchlorates have useful solubilities in the lower glycols. The proportions shown in Table I are in percent by Weight.

TABLE I Liquor A B C D E F G H Ethylene glycol 39 36 35. 5 35 34 33. 5 24. 5 24. 5 Calcium nitrate (technical) 48 38 37. 5 37 36 35. 5 30. 30. 0 Ammonium nitrate-.. 18 26 27. 0 26 26 25. 0 31. 30. 0 Sodium nitrate 2 4 6. 0 5. 0 5. 0 Formamide 9. 0 10. 6 Crystallization p nt, 114 108 114 108 101 112 118 111 TABLE II Liquor A B C D E Ethylene glycol 28.0 28 0 33.0 13-5 11-6 Diethylene glycol 5.0 4. 3 3. 6 Formarnide 15. 0 8.0 7. l Urea Calcium nitrate (technical) 30.0 30 0 30 0 16.0 19.0 Monomethylaminc nitrato 48.0 42.5 Ammonium nitrate 15. 0 15.0 15. 0 8. 0 14. 2 rs 12 t8 :1 1s y roxypropy gua Oxygen value 53 52 51 42 9 Crystallization point, F 58 68 52 77 63 All of the liquors shown in Table II possess lower oxygen balances compared with ethylene glycol or other glycols. The lower crystallization points, compared to the liquors of Table I, indicate an increased dissolution therein of useful oxygen-supplying salts at reduced temperatures.

The thickened glycol gel-phase of the present invention, preferably containing dissolved oxygen-supplying material, is used to form the thickened fluid matrix in gelatin and semi-gelatin explosive compositions containing particulate high energy sensitizers. The utility of this gel-phase in gelatin and semi-gelatin compositions devoid of liquid nitric esters is demonstrated in Table III below. The glycol-based liquors employed are liquors A and E shown in Table II above. The proportions shown in Table III are in percent by weight.

TABLE III A 13 o D E Formulation:

Pentacrythritol tetranitrate Trinitrotoluene Mcthylamine nitrate.-. 8. 0

Ammonium nitrate 6. 2

Sodium nitrate 2.0 Cobalt nitrate 2.0 Aluminium (paint pn'me pogder). 3.0 aif "'50 "Z0 20.0 H 1 1 5' y roxypropy guar... 0. 0. Density 1.38 1.25 1.13 27 1.24 Initiator 1 10 g. P in 1% cartridge. 2 10 g. P in 1% cartridge. 3 10 g. P in 2" cartridge. 4 SEB ea in 1%, cartridge.

*P =pentolite 60/40 PETN TNT.

The formulations shown in Table III were of an extrudable consistency similar to that of gelatin dynamite. It may be seen that the use of the thickened glycol gelphase permits the formulation of thickened or gelled explosives employing a variety of known high energy sensitizing materials.

The formulation recorded in Table IV below corresponds in consistency to the liquid nitric ester semi-gelatins known to the art. The known commercial semi-gelatins are cohesive, granular powders having a minor degree of tractability which is achieved by the inclusion of a small quantity of nitro-cotton along with the nitroglycerin sensitizer. The semi-gelatin of Table IV contains neither nitroglycerin nor nitrocotton. The proportions shown are in percent by weight.

TABLE IV Medium-fine water-moist PEIN 1 11.7 Flaked TNT 10.0 Ammonium nitrate:

Fine grain 46.8. Coarse grain 10.0. Sodium nitrate 15.0. Guar flour 2.0. Glycol liquor A containing 1% by weight hydrox- 4.5.

ypropyl guar plus anticaking additive. Oxygen balance 5.0. Density 1.4 g./cc. Initiation in 1% diameter cartridge One N o. 6 EB 0371'). Impact sensitivity with 5 kg. weight 45-50 inches.

1 Granular PEIN is normally handled in a water-moistened state for safety reasons.

The non-nitroglycerin semi-gelatin of. Table IV possesses the same physical characteristics as a commercial nitroglycerin-based semi-gelatin and may be cartridged in the same manner as is employed with the nitroglycerinbased product. It was found that the addition of a small quantity of anti-caking additive to the glycol liquor gelphase provided excellent antihardening characteristics for the final cartridged product even during storage at elevated temperatures. Similar compositions containing an aqueous gel instead of the glycol-based gel of the present invention harden overnight at 96 F. storage.

While the compositions shown in Tables III and IV employ as the sensitizer trinitrotoluene and pentaerythritol tetranitrate, methylamine nitrate and aluminium, other high energy sensitizers such as smokeless powder, nitrostarch, RDX, and the like may be employed with equal facility.

The quantities of thickened lower glycol gel-phase used in the explosive compositions of the invention will depend on the degree of plasticity desired in the final product. As noted heretofore, the ability of the preferred thickeners to gel a lower glycol is somewhat unpredictable in the presence of oxidizing salts and hence the provision of an adequate gel-phase is partly dependent on the kind of oxidizing salts which are present in the mixture. The quantities of the gel-phase employed must be somewhat arbitrary since presence of greater or lesser quantities of the other ingredients in the explosive mixture will be large determinant factors.

What we claim is:

1. A gelatinized explosive composition comprising a high energy sensitizer selected from particulate organic explosives, explosive amine nitrates and aluminium and from about 3% to about by weight of a non-explosive gel comprising at least one lower aliphatic glycol selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol and dipropylene glycol thickened with a material selected from the group consisting of hydroxyethyl and hydroxypropyl ethers of polysaccharides and mixtures thereof.

2. An explosive composition as claimed in claim 1 wherein the non-explosive gel contains at least one dissolved oxygen-supplying salt.

3. An explosive composition as claimed in claim 1 wherein the polysaccharide is selected from the group consisting of glucose polysaccharides, mannosepolysaccharides, galactose polysaccharides and mixtures thereof.

4. An explosive composition as claimed in claim 1 additionally containing oxygen-supplying and fuel ingredients.

References Cited UNITED STATES PATENTS 3,465,675 9/1969 Bronstein 149-44 X STEPHEN J. LECHERT, JR., Primary Examiner US. Cl. X.R. 

